Method for performing an upshift of an automatic transmission of a motor vehicle and motor vehicle

Abstract

The invention relates to a method for performing an upshift of an automatic transmission of a motor vehicle while the motor vehicle is driven by a prime mover and thereby accelerated, wherein the upshift is performed when a rotational speed of a shaft of the motor vehicle corresponds to a triggering speed. The triggering speed is calculated from a difference between a maximum rotational speed of the shaft and a calculated rotational speed range. The rotational speed range is calculated from a product of a shift time specified for the upshift and a determined current gradient of the rotational speed of the shaft. The rotational speed range or the rotational speed gradient is additionally multiplied by a factor which is calculated from a ratio between a maximum possible drive torque of the prime mover and a drive torque currently provided by the prime mover.

Description

[0001] The invention relates to a method for performing an upshift of an automatic transmission of a motor vehicle according to the preamble of claim 1. Furthermore, the invention relates to a motor vehicle.

[0002] DE 10 2007 045 339 A1 discloses a method for controlling an upshifting process in automatic transmissions, in which a shift point is determined based on an instantaneous speed gradient, an instantaneous speed, and a predetermined maximum target speed. DE 10 2008 010 280 A1 discloses a method for controlling a shifting process of automatic transmissions using an electronic control unit. Furthermore, DE 10 2004 061 079 A1 discloses a method for controlling a shifting process of automatic transmissions.

[0003] The object of the present invention is to create a method and a motor vehicle such that an automatic transmission of the motor vehicle can be shifted up particularly advantageously.

[0004] This problem is solved by a method with the features of claim 1 and by a motor vehicle with the features of claim 6. Advantageous embodiments with expedient further developments of the invention are specified in the remaining claims.

[0005] A first aspect of the invention relates to a method for performing an upshift of an automatic transmission (also referred to simply as a transmission) of a motor vehicle (also referred to simply as a vehicle) while the motor vehicle is being driven and thereby accelerated by its engine. This means that the upshift is performed while the motor vehicle is being driven and thereby accelerated by its engine. Acceleration of the motor vehicle is understood to mean that the speed of the motor vehicle, which is traveling at a certain speed, particularly forwards, increases, i.e., is increased by the propulsion of the motor vehicle.The term "upshifting" in an automatic transmission refers to the following: The automatic transmission has at least two selectable gears, namely a first gear and a second gear. The first gear has a first gear ratio. The second gear has a second gear ratio. The second gear ratio is, in particular, lower than the first gear ratio. The vehicle can be driven by the engine via the selected gear.During or through upshifting, the initially engaged first gear is disengaged and the initially engaged second gear is engaged, so that the drive engine initially propels the motor vehicle via the engaged first gear and then via the subsequently engaged second gear, in particular such that when the drive engine propels the motor vehicle via the engaged first gear, propulsion of the motor vehicle by means of the drive engine via the engaged second gear is omitted, and that when the drive engine propels the motor vehicle via the engaged second gear, propulsion of the motor vehicle by means of the drive engine via the engaged first gear is omitted.

[0006] In particular, the process is carried out by means of an electronic computing device, also referred to as a control unit or electronic control unit, which, for example, controls the automatic transmission to perform the upshift. In this process, the upshift is performed when the rotational speed of a shaft of the vehicle, specifically the current actual rotational speed, corresponds to a trigger speed, i.e., when the shaft's rotational speed reaches the trigger speed. In other words, the upshift is performed, that is, started or triggered, when the shaft's rotational speed reaches the trigger speed.In other words, the upshift is performed at a trigger point, that is, initiated or triggered. This trigger point is the point in time at which the shaft's rotational speed corresponds to the trigger speed, i.e., when the trigger speed is reached, particularly because the shaft's rotational speed increases as a result of the vehicle's propulsion. In this method, the trigger speed is calculated, particularly using the electronic computing device, from the difference between the maximum shaft speed and a calculated rotational speed gradient. The rotational speed gradient is calculated from the product of a predetermined shift time for the upshift, including any necessary times for torque transfer to other components, and a determined current gradient of the shaft's rotational speed, also known as the rotational speed gradient.

[0007] To make the upshifting particularly advantageous, the invention provides that the speed range or speed gradient is additionally multiplied by a factor. In other words, in a first embodiment, the speed range is multiplied by the factor, and in a second embodiment, the speed gradient is multiplied by the factor. Thus, in the first embodiment, the trigger speed is calculated from the difference between the maximum speed of the shaft and a product of the factor and the speed range, specifically by subtracting the product of the factor and the speed range from the maximum speed of the shaft.In the second variant, for example, the speed range is calculated from the product of the switching time and the product of the speed gradient and a factor. In other words, the speed range is calculated by multiplying the switching time by the current speed gradient and the factor. The factor is calculated directly or indirectly from the ratio of the maximum possible drive torque of the drive motor to the drive torque currently supplied by the drive motor, i.e., the applied drive torque. This means that the maximum possible drive torque is the highest torque that the drive motor can supply, particularly via the shaft.The currently applied drive torque, i.e., the drive torque currently provided by the drive machine, particularly via the shaft, is a torque that is currently provided by the drive machine, particularly via the shaft, especially to drive the motor vehicle.

[0008] The method according to the invention has the particular advantage that, with a comparatively low applied drive torque, i.e., with a comparatively flat current speed gradient, the upshifting is initiated, i.e., started, at low release speeds, thereby avoiding an excessively high shaft speed and any resulting reduction in the drive motor's speed, also known as derating. In other words, the method according to the invention avoids an undesirable, excessively high shaft speed and the resulting reduction in the drive motor's speed, thus also avoiding cumbersome implementations of the upshifting process.

[0009] The procedure, in particular the first variant of the procedure, is expressed below using formulas:

[0010] The ones with n auslös The specified trigger speed is calculated as follows: nauslo¨s=nmax−f∗Δnts

[0011] Here, n denotes max the maximum rotational speed of the shaft, f the factor and Δn ts the rotational speed range. The rotational speed range Δn ts This results in: Δnts=G*ts

[0012] This refers to ts The switching time and G represent the rotational speed gradient, and thus the gradient of the shaft's rotational speed. The rotational speed gradient G is given by: G=Δncurrent / Δt

[0013] Here, Δn denotes aktuell A difference, also referred to as a speed step, between a first value of the shaft's rotational speed and a second value of the shaft's rotational speed, where the shaft's rotational speed has the first value at a first time point and a second value at a second time point following the first. In particular, the difference Δn aktuell to: Δnaktuell=nn−nn−1

[0014] Here, n denotes n the second value of the rotational speed and n n-1 The second value of the rotational speed precedes the first value of the rotational speed in time. In particular, the rotational speed values, also referred to as rotational speed measurements, are measured values ​​that are measured and thus recorded by means of a rotational speed sensor. The rotational speed sensor, and thus the shaft, is located, for example, on or in a transmission output shaft of the automatic transmission or on a vehicle wheel, such that the shaft is, for example, an output shaft of the transmission and / or a shaft that is permanently and rotationally fixed to the vehicle wheel. In particular, the rotational speed of the shaft can therefore be the rotational speed of the vehicle wheel, also referred to as the wheel speed. Furthermore, Δt denotes a difference, also referred to as a time interval, between the aforementioned, different points in time, such that the difference Δt is, for example, as follows: Δt=tn−tn−1

[0015] Here, t denotes n the second point in time and t n-1 the first point in time that precedes the second point in time.

[0016] The maximum possible torque of the drive motor M max denoted by M, the current drive torque supplied by the drive motor, and thus the currently applied drive torque, is denoted by M. aktuell denoted. In one possibility, the factor f is: f=Mmax / Mcurrent

[0017] Then, in the first possibility, the factor is a so-called multiplication factor. To allow for variation of this factor, it can be varied using another parameter or a characteristic curve that shows a dependency on, for example, a rotational speed, a current drive torque, a maximum possible torque, the aforementioned multiplication factor, or similar parameters.

[0018] In a second possibility, the factor f is: f=Makteull / Mmax

[0019] In the second possibility, the factor is a moment factor, which is also M f is designated. Subsequently, that is, after calculating the moment factor M f For example, this moment factor M f via a datable characteristic curve, which for example maps the torque factor via the multiplication factor or the dependencies already mentioned in the first possibility, the multiplication factor is determined, with which, for example, the rotational speed stroke is multiplied.

[0020] It is evident that the upshifting, or rather its initiation or start, depends on the speed gradient and the shift time required for the upshift, particularly until the maximum speed is reached or the speed gradient changes. However, if, for example, the speed gradient suddenly increases shortly before reaching the maximum speed, especially if acceleration initially occurs with a relatively small speed gradient followed by depressing the accelerator pedal, thereby increasing the applied torque, then, if no appropriate countermeasure is taken, the upshifting may be initiated too late. Consequently, the drive motor's speed is reduced to prevent damage. This can lead to an uncomfortable upshifting process or other undesirable effects. The invention now prevents this.For example, by multiplying the speed range or speed gradient by a factor, a virtual speed gradient is determined or estimated, based on the current speed gradient at the currently set drive torque and the maximum possible drive torque. This allows for the determination of an advantageous time for upshifting, i.e., for initiating, beginning, triggering, or starting the upshift. The basis is, for example, the initially current speed gradient with which acceleration occurs from the current point in time. A quotient in the form of the factor is calculated from the maximum possible drive torque (front and / or rear axle) and the currently applied drive torque. The factor, or its value, can range from 0 to 1 inclusive. The factor, or the quotient, is 0 if no positive torque is applied.The factor, or quotient, is 1 when the currently applied drive torque corresponds to the maximum possible drive torque. Depending on this factor, which then represents a measure of the currently set drive torque relative to the maximum drive torque, a factor, particularly in the form of a multiplication factor, can be determined via a characteristic curve. This factor is then used, for example, to multiply the current speed gradient. The factor, specifically the multiplication factor, can be 4, for instance, when acceleration occurs at 25 percent of the maximum possible drive torque, meaning when the currently applied drive torque is 25 percent of the maximum possible torque. The multiplication factor is 2 when acceleration occurs at 50 percent of the maximum possible drive torque, meaning when the currently applied drive torque is 50 percent of the maximum possible drive torque.The multiplication factor is 1 when accelerating at full load, meaning when the current drive torque corresponds to the maximum possible drive torque. Multiplying the speed gradient by this factor effectively amplifies the speed gradient. This ensures that, even with very high potential acceleration reserves, upshifting is always initiated in a timely manner, thus minimizing the risk of excessively high shaft speed due to a delayed upshift. A reduction in acceleration torque or acceleration is then unnecessary, allowing the vehicle to always accelerate at maximum possible speed. Therefore, torque reduction or engine speed limiting is advantageously only required in exceptional circumstances.

[0021] In order to perform the upshifting particularly advantageously, a shaft of the drive machine is used as the shaft.

[0022] Another embodiment of the invention is characterized in that an electric machine is used as the drive motor, by means of which the motor vehicle is, for example, driven purely electrically. This allows the upshifting to be carried out particularly advantageously.

[0023] In order to make the upshifting particularly advantageous, a further embodiment of the invention provides that the drive motor and the automatic transmission form an integral unit.

[0024] It has proven particularly advantageous if the integrated unit is designed as a hybrid transmission or as an electric axle drive unit. This allows for particularly efficient upshifting.

[0025] A second aspect of the invention relates to a motor vehicle, also referred to simply as a vehicle, and preferably configured as a motor car, in particular as a passenger car, which is configured to carry out a method according to the first aspect of the invention. Advantages and advantageous embodiments of the first aspect of the invention are to be regarded as advantages and advantageous embodiments of the second aspect of the invention, and vice versa.

[0026] Further advantages, features, and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and combinations of features mentioned above in the description, as well as those mentioned below in the figure description and / or shown in the figures alone, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0027] The drawing shows in: Fig. 1 a diagram illustrating a method for performing an upshift of an automatic transmission of a motor vehicle, wherein Fig. 1. This serves to explain the background of the invention; and Fig. 2. Another diagram to further illustrate the procedure.

[0028] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0029] Based on Fig. 1 and Fig. 2. A method for performing an upshift of an automatic transmission of a motor vehicle is described below, wherein the upshift and thus the method is carried out while the motor vehicle is driven and thereby accelerated by means of a drive motor of the motor vehicle. Fig. 1 and Fig. Figure 2 shows a respective diagram, on whose respective abscissa 10 the time t is plotted, specifically with respect to the image plane of Fig. 1 and Fig. 2 increasing from left to right. On the respective ordinate 12 of the respective diagram, a rotational speed of a shaft of the motor vehicle, denoted by n, is plotted, specifically relative to the image plane of Fig. 1 and Fig. 2 increasing from bottom to top. In particular, the shaft is a shaft of the drive machine which, for example, provides a drive torque, also referred to simply as torque or drive torque, during the process, by means of which the motor vehicle is driven and, in particular, accelerated.

[0030] In Fig. 1 is a first curve V1, a first time-dependent curve of the rotational speed over time. A second curve V2 is a second time-dependent curve of the rotational speed over time. In Fig. Figure 1, denoted by n_max, represents a maximum shaft speed that can be specified or predetermined. Figure t_schalt represents a predefined or predetermined shift time required to perform the upshift. Ideally, the upshift should be performed in such a way that the vehicle can accelerate as desired and / or sufficiently, the upshift should be smooth, and the current shaft speed (represented as the actual speed), which rotates around an axis relative to the drive motor housing, should not exceed the maximum speed. This prevents an undesirable reduction in the drive motor's speed, also known as derating.

[0031] The switching time is defined at the transmission level and stored, for example, in the electronic memory of an electronic processing unit (EPU) that executes the process. Alternatively, the switching time can also be transmitted via a CAN bus. Specifically, the switching time defines the time required from the activation of the upshift (also referred to as the switching trigger) until a reversal point of the rotational speed gradient (also referred to as the speed gradient), or until the point at which the speed gradient is zero. The speed gradient is transmitted, for example, via a data bus of the vehicle, particularly a CAN bus, or alternatively, determined in the EPU using the rotational speeds transmitted via the CAN bus.The respective curves V1 and V2 have a corresponding trigger speed D1 and D2, at which the upshift should be initiated to perform the upshift efficiently and, in particular, to prevent the shaft speed from exceeding the maximum speed. A first speed gradient of curve V1 is denoted by D_flat, and a second speed gradient of curve V2 is denoted by D_steep. It can be seen that the speed gradient of curve V2 is greater or steeper than the speed gradient of curve V1, whose speed gradient is flatter or less than that of curve V2. This can be seen from... Fig. In particular, it is important that with a steep speed gradient, the upshift should be triggered earlier than with a flat speed gradient, in order to avoid the shaft speed exceeding the maximum speed.

[0032] If, for example, acceleration occurs with a shallow speed gradient and thus a low load until just before the maximum permissible speed, and the load—that is, the drive torque supplied by the drive motor—and thus the speed gradient is increased shortly before the current shaft speed reaches the maximum speed (for example, before or after the start of an upshift), then, if no countermeasure is taken, the actual shaft speed may exceed the maximum speed, since the upshift should have started earlier. Exceeding the maximum speed due to the actual shaft speed is also referred to as overspeed.If overspeed occurs, the drive motor's torque must be significantly reduced to prevent undesirable effects such as damage. However, this can lead to insufficient acceleration and / or upshifts with inadequate shift quality. This can now be avoided by this method. In this method, the upshift is initiated when the current shaft speed equals the trigger speed, i.e., when the trigger speed is reached. The trigger speed is calculated as the difference between the maximum shaft speed and the calculated speed range.The speed gradient is calculated as the product of the shift time specified for upshifting and the determined current speed gradient (gradient of the shaft speed). Furthermore, the speed gradient is multiplied by a factor calculated from the ratio between the maximum possible drive torque of the drive motor and the drive torque currently provided by the drive motor, specifically intended for propelling the vehicle. For example, if the drive torque currently provided by the drive motor, specifically intended for propelling the vehicle, is 50 percent of the maximum possible drive torque of the drive motor, the resulting acceleration is characterized by a flat speed gradient, yielding, for example, the speed gradient D_flat.When the motor vehicle is accelerated with the current drive torque corresponding to the maximum possible drive torque, the speed gradient is twice as large as when the drive torque currently provided by the drive engine and intended to drive and thus accelerate the motor vehicle corresponds to 50 percent of the maximum possible drive torque of the drive engine.

[0033] Also in Fig.Figure 2 illustrates two time-dependent profiles, V3 and V4, of the shaft's rotational speed. Profile V4 results when the vehicle is accelerated with the drive torque currently supplied by the engine, which, in particular, corresponds to at least substantially 50 percent of the maximum possible torque. The described method essentially calculates or generates a speed reserve D_Vorhalt, whereby the trigger speed, denoted D3, is obtained by subtracting this speed reserve D_Vorhalt from the maximum shaft speed.The V3 process occurs when the vehicle is initially accelerated with the current drive torque, which is 50 percent of the maximum possible drive torque, and when, at the point in time when the upshift is initiated and the shaft speed therefore corresponds to the trigger speed D3, the driver depresses the accelerator pedal, thus requesting an increase in the drive torque provided by the engine and intended to propel the vehicle. It is evident that despite this increase in drive torque, the upshift is performed due to the speed lead D_lead, without the shaft speed exceeding the maximum speed. The shift is triggered based on the speed lead that would result at full load, i.e., during acceleration under full load.The trigger speed D3 is thus calculated by subtracting the speed lead D_lead from the maximum speed n_max. The speed lead D_lead is obtained by multiplying D_flat by a factor that, for example, is 2 if the current drive torque is 50 percent of the maximum possible drive torque. In other words, the speed lead D_lead is obtained by multiplying the switching time by 2 and the current speed gradient. Using the speed gradient and the factor also has the advantage of being independent of the current gradient or vehicle mass. The current speed gradient is determined by the current environmental conditions, and as long as these remain unchanged, the acceleration is proportional to the drive torque. Reference symbol list 10 Abscissa 12 ordinates D1 Release speed D2 trigger speed D3 trigger speed V1 progress V2 progress V3 progress V4 history n rotational speed t time n_max maximum speed t_switch switching time D_flat speed range D_steep speed range D_Prelay Speed ​​Prelay

Claims

[1] Method for performing an upshift of an automatic transmission of a motor vehicle while the motor vehicle is being driven and thereby accelerated by means of a drive engine, wherein: - the upshift is performed when a rotational speed (n) of a shaft of the motor vehicle corresponds to a trigger speed (D1, D2, D3); - the trigger speed (D1, D2, D3) is calculated from a difference between a maximum speed (n_max) of the shaft and a calculated speed stroke (D_flat, D_steep); and - the rotational speed range (D_flat, D_steep) is calculated from a product of a switching time (t_switch) specified for upshifting and a determined current gradient of the rotational speed (n) of the shaft; characterized by, that the speed range (D_flat, D_steep) or the speed gradient is additionally multiplied by a factor which is calculated from a ratio between a maximum possible drive torque of the drive machine and a drive torque currently provided by the drive machine. [2] Method according to claim 1, characterized by , that the shaft is a shaft of the drive machine. [3] Method according to claim 1 or 2, characterized by , that an electric machine is used as the drive machine. [4] Method according to any one of the preceding claims, characterized by that the drive motor and the automatic transmission form an integral unit. [5] Method according to claim 4, characterized by that the integral unit is designed as a hybrid transmission or as an electric axle drive device. [6] Motor vehicle designed to carry out a method according to any of the preceding claims.

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